Relations between Walleye (Sander vitreus) Recruitment and Spawning Habitat in Northeastern Wisconsin Lakes
File(s)
Date
2010-12Author
Rammer, Gina M.
Publisher
University of Wisconsin-Stevens Point, College of Natural Resources
Metadata
Show full item recordAbstract
The addition of spawning habitat to increase walleye (Sander vitreus) recruitment has
been used as a management tool in many north temperate lakes for decades. However, a
previous assessment of 20 artificial spawning habitat projects in northern Wisconsin
showed that few projects were successful in increasing abundance of age-0 walleyes.
Poor reef design or the existence of recruitment-limiting factors unrelated to spawning
habitat such as stock size, species composition, prey availability, and spring weather
patterns are likely more important factors in these systems. The objectives of my study
were to: 1) develop an accurate and efficient standardized method to measure walleye
spawning habitat in lakes without conducting a time consuming assessment of all
nearshore habitat and 2) determine if a relation between walleye recruitment, defined by
fall age-0 walleye abundance, and spawning habitat exists in naturally recruiting north
temperate lakes. Twenty study lakes with varying amounts of walleye spawning habitat
and recruitment patterns in northeastern Wisconsin were chosen to be measured for
spawning habitat and walleye recruitment. To develop a standardized sampling method,
walleye spawning habitat was measured using three experimental methods: 1) littoral
zone habitat was measured along 250 random transects, 2) visible gravel/cobble segments
were measured from a boat at the shoreline-water interface, and 3) the length of actual
spawning habitat, defined by criteria developed from previous resource selection
functions as ≥ 50% gravel and/or cobble substrate with low embeddedness, was measured
along shoreline areas. When compared to the criterion-based, direct habitat
measurement, a random transects method yielded the most accurate index of walleye
spawning habitat. The boat measure of spawning habitat, however, was only weakly
correlated with the direct measure, suggesting that this method should only be used, at
best, as a crude index of total spawning habitat. Average age-0 walleye abundance was
weakly related to total spawning habitat (m2), although no relation was found when data
were corrected for lake size. Average adult walleye abundance was found to be related to
total spawning habitat (m2), as was average adult abundance/ha and spawning habitat
(m2)/ha. Substrate variable analysis showed that age-0 walleye abundance was weakly
negatively correlated with fine organic matter and adult walleye abundance was related to
the percent gravel substrate present, as was adult walleye abundance/ha. Lake size was
weakly related to adult abundance and total spawning habitat (m2) but was not related to
age-0 abundance. This study increases our understanding of how critical habitat may
limit walleye populations and could be used in the development of spawning habitat
protection strategies. It does not appear that the addition of spawning habitat to a poorly
recruiting system will likely increase age-0 walleye. The weak correlations between age-
0 walleye abundance and available spawning habitat and limited study lakes (N=20) also
suggest future research be done, utilizing the same methods, to increase the sample size.
Future spawning habitat studies should also include an evaluation of other important
recruitment-limiting factors, like fish community structure and water quality.